Unfurlable structure including coiled strips thrust launched upon tension release



. Jan- 17, 1967 L. E. HoBLxN 3,299,431

UNFURLABLE STRUCTJRE INCLUDING COILED STRIPS THRUST LAUNCHED UPON TENSION RELEASE Filed Feb. l0, 1964 V ELECTRICAL "V" 50u/ece l 56 35 55 /7 54 /8 6 5 7 -a l/ /62 V4 /NA a 33 ff; m a? j ,//f f/ am@ @magma/m 24 la, /3 2 kl l Il' ,4 /4 a VWM j 3 Fg Z INVENTOR Leaser E #obli/7 GENT United States Patent O 3,299,431 UNFURLABLE STRUCTURE INCLUDING COILED STRIPS THRUST LAUNCHED UPON TENSION RELEASE Lester E. Hoblin, Fairfax County, Va., granted to National Aeronautics and Space Administration under the provisions of 42 U.S.C. 2457(d) Filed Feb. 10, 1964, Ser. No. 343,760 8 Claims. (Cl. 343-823) y This invention relates in general to antennas of the whip variety and in particular to extensible whip antennas.

Since the introduction of unfurlable whip -antennas by R. B. Bla-ckmore, to whom U.S. Patent No. 2,157,278 was granted on May 9, 1939, many have endeavoured to perfect a metallic strip sufficiently resilient to permit extensive deformation of the strip over extended periods of time without deterioration of the resilient properties thereof. Now that a metallic strip having such resilient properties is available, unfurlable whip antennas have been recognized as practical mechanical structures and considerable effort has been expended to devise means for transposing the deformation and the extension.

In many extensible antenna applications, particularly in spacecraft applications, weight, size and power requirements are especial-ly critical. Often environmental factors must be controlled in such applications, and it may be necessary, for example, to employ nonmagnetic materials exclusively. Moreover, it is generally essential that the structure afford a significant rigidity and durability in its extended state. Most prior art -devices which require both extension and retraction anchor the deform reel in the manner disclosed by Blackmore, and the metal strip is extended and retractedby rotation of the reel, usually by means of an electrical motor system. In the case'of an extension without retraction, either end may be anchored, of course, and one prior are device anchors the deform unit, a hollow cylinder wherein the furled metallic element is stored and employs a sideways ejection such that the fully extended antennais pivoted into fin-al position. Another more complex prior art device anchors the free end of each of two metallic elements which are spun upon ejection and the deform unit, a uniqueV reel with conical side cheeks isv adapted to serve as a centrifugal brake acting differentially to control the rate of ejection.

Each of these prior art extensible antenna ejection devices has found some utility in selected applications but few, if any, devices ofthis variety meet the demands of outer space. In particular, it has been found lthat the pivot features of one prior art device often presents an electrical and a mechanical problem in reliability. Also, the unique reel assembly, necessary to the free extension unit described above, introduces a weight complication which precludes its applicationpin many instances.

It will be appreciated that Aa lightweight, reliable extensible antenna is.l needed and would be welcomed as a significant advancement of the art. Accordingly:

It is an object of this invention to provide an extensible dipole antenna which is relatively lightweight.

It is another object of this invention to provide an extensible dipole -antenna in which the ejection means may be of nonmagnetic material.

It is also an object of this invention to provide an extensible -dipole antenna wherein no readjustment of element orientation is required upon rfull extension of the antenna. f

It is a further object of this invention to provide an extensible dipole antenna with a rigid Xed electrical connection upon extension.

It is still another object of this invention to provide an extensible dipole antenna wherein a positive ejection of the antenna elements is assured.

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Other objects of the invention will become apparent upon a more comprehensive understanding of the invention for which reference is had to the following specification and drawings wherein:

FIGURE 1 is a detailed showing of one embodiment of this invention in readiness for unfurlment.

FIGURE 2 is a showing of the embodiment of FIG- URE l in its unfurled state.

Briefly, the device of this invention is an extensible dipole antenna employing a naturally tubular metallic strip element which is deformable into a transverse coil form and is sufficiently resilient to revert back to its natural configuration. The device affords a positive action ejection of the strip element in coil form by release of a loaded compression spring means whereby the resilience of the strip is implemented.

Referring now to the drawings,

The embodiment of this invention shown in FIGURE l includes a base and center -column section 11 which is secured by conventional means to the support member 12 which may be, for example, the spear boom of a missile intended for satellite application.

In accordance with the invention, at least three pairs of transverse members, the pair 13 and 14, the pair 15 and 16, and the pair 17 and 18, having end sections, 13a and 14a, 15a and 16a, 17a and 18a, respectively, are disposed in parallel relation to substantially define a plane and are attached to the center column section 11 such that the end sections of each pair are substantially equidistant the center column section 11 and each member is in substantially perpendicular relation with respect thereto. It will be appreciated, of course, that in the depicted embodiment the pairs of members, 15 and 16, and 17 and 18, may in actuality be a single continuous member of conductive or nonconductive material which passes through the center column section. The pairs of members 13 and 14, however, are connected to the dipole elements 21 and 22 which, of course, must be electrically isolated. Consequently, if a single continuous member is t0 be substituted for the pair 13 and 14, the member must be of a nonconductive material.

As shown in the embodiment of FIGURE 1, the pair of members 15 and 16 may be longer than the pair of members 13 and 14, and the pair of members 17 and 18 may be longer than the pair of members 15 and 16. In this length relationship, the coiled dipole elements 21 and 22 may be nested slightly beneath the respective member of pair 17 and 18 and substantially adjacent the respective end section of pair 15 and 16 by detent means 23 and 24, respectively. l

It will be appreciated that various forms of detent means may be employed with the device of this invention to contain the dipole element in coiled' form. In the illustrative embodiment, each detent means comprises a string section secured at one end as indicated at 31 to the respective end sections 17a and 18a with the other end tied to an interrupter means 32 such that upon interruption the string section no longer restrains the coiled dipole element, and it is free to unfurl.

In this embodiment, the interrupter means 32 comprises a link of fuseable wool 33 in contiguous relation with the fuseable wire. Firing means 34 may be an electrical source, as shown, which effectively ignites the wool to separate the loop and thus disable the detent means 23 and 24 simultaneously upon the activation of switch means 34 by remote control means, not shown.

In accordance with the invention compression springs 35 and 36 are disposed about the transverse members 15 and 16, respectively. Since the no 'load length of each of the springs 35 and 36 is substantially greater than the length of its respective transverse member, it will be seen that with the coiled dipole element in readiness as shown, the springs 35 and 36 are under considerable tension. Thus, when the detent means 23 and 24 are disabled, the force of the springs 35 and 36 ejects the coiled dipole elements simultaneously.

The coiled dipole elements 21 and 22 are electrically and mechanically secured at their free end to respective members of the pair of transverse members 13 and 14. As in the device described by Blackmore in his aforementioned patent, the metallic strips, which form each of the dipole elements 21 and 22, have a natural circular cross-section with a substantial overlap. In addition, these metallic strips are characterized by a high resiliency which permits nonpermanent deformation into coil form. This type of material is generally of the alloy variety and may be formed by various manufacturing techniques generally including heat treatment at one or more stages.

FIGURE 2 is illustrative of the device of FIGURE l after the detent means has been disabled and the elements 21 and 22 have been unfurled. In this illustration, the unfurlable antenna device is disposed in the nose end of a rocket or other space vehicle and the elements 21 and 22 are extended in substantially perpendicular relation to lche general axis of the vehicle. It will be noted that the compression spring means are missing in the embodiment depicted in FIGURE 2. These ejection means may be ejected in the course `of the coiled member release or otherwise. It is, of course, within the purview of this disclosure to employ suitable detaining means, not shown, in the event release of the ejection means would be undesirable. Further, in this illustration the elements 21 and 22 and the central support member to which they are attached are shown without electrical insulation means therebetween. It will be appreciated that some electrical separation is essential to most applications of the device of this invention and that this may be accomplished as shown in the embodiment of FIGURE l or otherwise.

The dipole elements 21 and 22 may be coiled either in the direction relative to the natural circular cross-section shown in the drawing or in the opposite direction, provided, of course, the strip material has sufficient resiliency. It has been found, however, that coiling in the direction shown in the drawing is to be preferred in most appli-cations.

It will be appreciated that the depicted compression spring means for initial ejection of the coiled elements 21 and 22 is not essential to the operation of the device and that various other spring loaded means for ejection secured by the detent means shown or by other suitable means, for example, a cooperative latching mechanism, are Within the purview of this disclosure.

Likewise, it is not essential that the detent means be released by remote control. In the event direct control means are employed, it will be appreciated that a wide variety of means may be employed to release the detent means.

Furthermore, it is not essential to this invention that two members be released or that the release of members occurs simultaneously. Thus it is within the purview of this disclosure to employ a separate detent means for each coiled member and to cause the release of members in any selected order, if desired.

Moreover, the device of this invention is not restricted to extensible antennas nor to electrical applications in general, and the unique concept embodied therein is applicable to a -Wide variety of uses including decorative display systems, direction indicator means and the like.

Finally, this invention is to be limited only by the scope of the claims appended hereto.

What is claimed is:

1. An unfurlable structure comprising a central support member, a plurality of ribbon like flexible strip elements each having a lcoiled portion and a free end portion disposed with the free end thereof directed toward said central support member; a like plurality of rod means extended from said central support` member in selected directions; means for attaching said free end of each of said strip elements to a respective rod means in said plurality thereof such that the axis of each coiled portion and its respective rod means are in a transverse relation; each of said elements having a selected length and width and characterized by a stable circular cross-section with a substantial overlap and by a resiliency such that said stable circular cross-section may be readily restored subsequent to deformation of said strip element into coil form; detent means adapted to maintain said coiled portion of said elements at a selected distance from said central support member; tension loaded ejection means interposed said coiled portion of each of said strip elements and said central support member and adapted to provide a thrust force therebetween upon tension release; and detent release means adapted to free said coiled portion of said strip element such that said tension release occurs.

2. An unfurlable structure as defined in claim 1 wherein said exible strip elements are adapted as antenna elements.

3. An unfurlable structure as dened in claim 2 wherein said plurality of exible strip elements is an even number plurality, said strip elements are paired and each pair is disposed in opposite relation about said central support member and said detent release means are adapted to release respective elements of each of said pairs thereof in time coincidence such that said thrust for-ce of respective ejection means directed toward said central support means is substantially counter-balanced.

4. An unfurlable structure as defined in claim 2 wherein at least a portion of said tension loaded ejection means are compression spring means and said detent means are adapted to maintain said spring means under compresslon.

5. An unfurlable structure as deiined in claim 3 wherein at least a portion of said tension loaded ejection means are compression spring means and said detent means are adapted to maintain said spring means under compression.

6. An unfurlable structure as defined in claim S wherein said detent means are strap means.

7. An unfurlable structure as defined in claim 6 wherein respective strap means of respective strip elements in each pair thereof are interlinked and said detent release means is operative to interrupt the linking therebetween.

8. An unfurlable structure as dened in cla-im 7 wherein `said detent release means is a fuseable lmaterial in close proximity to said strap means of respective strip elements in each pair such that ignition of sa-id iuseable material alords interruption of said linking therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,085,585 6/1937 Hamilton 343-877 2,212,128 8/1940 Richter v.. 343-902 Y2,569,810 lO/1951 Hamel et al. 343-877 FOREIGN PATENTS 800,738 5/1936 France.

ELI LIEBERMAN, Primary Examiner. R. F, HUNT, JR., Examiner, 

1. AN UNFURLABLE STRUCTURE COMPRISING A CENTRAL SUPPORT MEMBER, A PLURALITY OF RIBBON LIKE FLEXIBLE STRIP ELEMENTS EACH HAVING A COILED PORTION AND A FREE END PORTION DISPOSED WITH THE FREE END THEREOF DIRECTED TOWARD SAID CENTRAL SUPPORT MEMBER; A LIKE PLURALITY OF ROD MEANS EXTENDED FROM SAID CENTRAL SUPPORT MEMBER IN SELECTED DIRECTIONS; MEANS FOR ATTACHING SAID FREE END OF EACH OF SAID STRIP ELEMENTS TO A RESPECTIVE ROD MEANS IN SAID PLURALITY THEREOF SUCH THAT THE AXIS OF EACH COILED PORTION AND ITS RESPECTIVE ROD MEANS ARE IN A TRANSVERSE RELATION; EACH OF SAID ELEMENTS HAVING A SELECTED LENGTH AND WIDTH AND CHARACTERIZED BY A STABLE CIRCULAR CROSS-SECTION WITH A SUBSTANTIAL OVERLAP AND BY A RESILIENCY SUCH THAT SAID STABLE CIRCULAR CROSS-SECTION MAY BE READILY RESTORE SUBSEQUENT TO DEFORMATION OF SAID STRIP ELEMENT INTO COIL FORM; DETENT MEANS ADAPTED TO MAINTAIN SAID COILED PORTION OF SAID ELEMENTS AT A SELECTED DISTANCE FROM SAID CENTRAL SUPPORT MEMBER; TENSION LOADED EJECTION MEANS INTERPOSED SAID COILED PORTION OF EACH OF SAID STRIP ELEMENTS AND SAID CENTRAL SUPPORT MEMBER AND ADAPTED TO PROVIDE A THRUST FORCE THEREBETWEEN UPON TENSION RELEASE; AND DETENT RELEASE MEANS ADAPTED TO FREE SAID COILED PORTION OF SAID STRIP ELEMENT SUCH THAT SAID TENSION RELEASE OCCURS. 